Biomass-Derived Carbon Heterostructures Enable Environmentally Adaptive Wideband Electromagnetic Wave Absorbers

Although advances in wireless technologies such as miniature and wearable electronics have improved the quality of our lives,the ubiquitous use of electronics comes at the expense of increased exposure to electromagnetic(EM)radiation.Up to date,extensive efforts have been made to develop high-performance EM absorbers based on synthetic materials.However,the design of an EM absorber with both exceptional EM dissipation ability and good environmental adaptability remains a substantial challenge.Here,we report the design of a class of carbon heterostructures via hierarchical assembly of graphitized lignocellulose derived from bamboo.Specifically,the assemblies of nanofibers and nanosheets behave as a nanometer-sized antenna,which results in an enhancement of the conductive loss.In addition,we show that the composition of cellulose and lignin in the precursor significantly influences the shape of the assembly and the formation of covalent bonds,which affect the dielectric response-ability and the surface hydrophobicity(the apparent contact angle of water can reach 135°).Finally,we demonstrate that the obtained carbon heterostructure maintains its wideband EM absorption with an effective absorption frequency ranging from 12.5 to 16.7 GHz under conditions that simulate the real-world environment,including exposure to rainwater with slightly acidic/alkaline pH values.Overall,the advances reported in this work provide new design principles for the synthesis of high-performance EM absorbers that can find practical applications in real-world environments.

An angle-insensitive electromagnetic absorber enabling a wideband absorption

Electromagnetic(EM)wave absorbers with wideband absorption capability are proposed as a strategy to mitigate environmental pollution by EM waves.However,designing an EM absorber with its performance capacity independent of the EM wave incident angle remains elusive to date.Resolving this challenge requires development of EM absorbers whose EM absorption performance is insensitive to the EM wave incident angle.Herein,we synthesized EM absorbers with a variety of structures with different symme-tries(including micro-/nanospheres,nanoflakes and nanotubes)to study the effect of the EM absorbers’structure and the EM wave incident angle on the EM absorption performance.Our analysis reveals that non-magnetic EM absorbers with spatially symmetric nanostructures exhibit excellent EM wave incident angle-insensitivity.Finally,we demonstrate that a class of non-magnetic EM absorbers made from bam-boo derived-carbon nanospheres exhibit EM incident angle-insensitivity and wideband EM absorption performance with an effective absorption band up to 3.5 GHz when the thickness is 1.4 mm,a signif-icant improvement from prior studies which used thicknesses as high as 3-4 mm for comparable EM absorption performance.